1. Field of the Invention
The present invention generally related a method of manufacturing a semiconductor device, and more particularly, to a method of manufacturing a semiconductor device having a storage node.
2. Description of the Background Art
A capacitor including a storage node as a constituent element has been used for a memory IC, e.g., DRAM. The capacitor (hereinafter referred to as a "storage node capacitor") comprises a storage node and a cell plate, both of which are formed from base material such as polysilicon, and a dielectric film which is interposed between the storage node and the cell plate and keeps them isolated from each other. With such a configuration, electric charges can be charged by the storage node and the cell plate by applying a voltage between them.
It is effective to ensure a larger surface area of the storage node capacitor in its occupation area for rendering the storage node capacitor compact. A greater surface area of the storage node can be ensured by forming the storage node into, e.g., the shape of a cylinder. Thus, a structure including a storage node formed into a cylindrical shape has been known as a structure of a storage node capacitor.
FIG. 10 shows the structure of a known cylindrical storage node 10. The storage node 10 shown in FIG. 10 can be provided by executing a series of operations described below.
(1) Formation of a sacrificial oxide layer (not shown) on a silicon oxide film 12; PA1 (2) Formation of a contact hole 14 which passes through the sacrificial oxide layer and the silicon oxide film 12; PA1 (3) Formation of a storage node contact 16 within the contact hole 14; PA1 (4) Formation of a space used for forming a storage node 10 by removing the sacrificial oxide layer in a cylindrical form; PA1 (5) Formation of the storage node 10 into a cylindrical shape within the space; and PA1 (6) Formation of the storage node 10 into a state shown in FIG. 10 by etching away the sacrificial oxide layer surrounding the storage node.
It is effective to form the storage node 10 into an elongated shaped for providing a compact storage node capacitor having a large capacity and having the aforementioned conventional structure. However, the narrower the storage node 10, the more the node becomes apt to tilt. Particularly, in the foregoing existing method, an etching effect is sometimes exerted on the silicon oxide film 12 as well as on the sacrificial oxide layer.
If an etching effect is exerted on the silicon oxide film 12, the adhesion between the bottom surface of the storage node 10 and the silicon oxide film 12 is deteriorated, thus rendering the storage node more likely to tilt. For this reason, so long as the existing manufacturing method is used, it is difficult to make the storage node 10 compact while maintaining a high yield. More specifically, it is difficult to make a memory IC compact while maintaining a high yield.